Three areas of research concerning peripheral nerve fiber regeneration were investigated. In one study in rats, denervated nerve stumps were sutured into opposite ends of 10-mm long impermeable silicone chambers. This surgical procedure was designed to determine whether nonneuronal cells from the ends of the nerve stumps (i.e., Schwann, endothelial and fibroblasts) would proliferate and migrate into the chamber and form a tissue cable in the absence of regenerating axons. Electron microscopy revealed that after four weeks cables formed in chambers, and that all nonneuronal cell types contributed to cable formation. However, cables formed only in chambers that were filled, at the time of surgery, with dialyzed plasma and not phosphate-buffered saline. Schwann cells in aneural cables were enclosed within basement membrane. Heretofore, it was believed that only axons induced basement membrane formation by Schwann cells. We now plan to anastomose a normal proximal nerve stump (i.e., one that contains axons) to aneurally formed cables to determine if these cables can support axonal regeneration through them. In another study, we attempted to cryopreserve nerves of rats for later use as nerve grafts. Peroneal nerves were successfully cryopreserved in a mixture of dimethyl sulfoxide and formamide (DF). Nerves in DF were stored in liquid nitrogen up to five weeks and survived subsequent transplantation as manifested by the presence in them of Schwann and perineurial cells and an endoneurial vasculature. Host axons were able to regenerate through 4-5 cm lengths of cryopreserved nerve rafts. However, when employed as allografts, cryopreserved nerves were rejected by normal, untreated rats but not by rats immunosuppressed with the drug cyclosporine . If human nerves can be cryopreserved and their rejection prevented by cyclosporine therapy, it should be possible to create human nerve banks from which grafts can be obtained to repair gaps in injured peripheral nerves. Pigeons were utilized to elucidate how the degenerating olfactory pathway prepares itself for olfactory axonal growth. The factor s stem is unique because after injury, olfactory neurons die and are replaced from stem cells that differentiate into new neurons. It is important to determine how the axons of these new neurons grow back into their target tissue in the central nervous system (CNS), the olfactory bulb. After unilateral olfactory nerve transection, olfactory axons disappeared and their supporting cells in the degenerating nerve stump arrange themselves into two concentric tube-like channels. The smaller, inner channel consisted of dramatically shrunken basement membrane which enclosed ensheathing (possibly Schwann) cells whereas the larger, outer channel was composed of fibroblast-like cells that lacked basement membranes. Further electron microscopic study should reveal which tube growing olfactory axons are utilized for growth into the CNS.